The present invention relates to an apparatus and method for controlling motive machines and their attendant features. More specifically, the present invention relates to an apparatus and method for controlling motive machines through the use of force rather than displacement.
The primary objective of any human interface to a machine is to allow a person to interact with the machine in the most natural and convenient way possible while allowing for precise control of all the machine's functions. Except for work done in the field of virtual reality, current interfaces between man and machine have not been drastically changed over the last several decades. The current technologies for controlling motive machines are all centered on the use of displacement is the primary means of control.
Typically, small displacement in an interface to control a machine translates to low speed, low power, slow rate of turn, low lift, etc. for the controlled machine. While a large displacement of the interface translates to high speed, quick rate of turn, high lift power, etc. For example, to control the speed of an automobile an accelerator pedal is used. To drive the car slowly, the pedal is depressed a short distance towards the floorboard of the car. To drive the car faster, the pedal is depressed further (closer towards the floorboard of the car). The factor that controls the speed of the car is the amount of displacement of the accelerator pedal towards the floor of the car.
The problem with current technologies is that the use of displacement to control the movement of an object is fundamentally unnatural to humans. The general manner in which a person moves an object is to apply force in the direction of the desired movement. For example, if a man wishes to lift a large rock, he grasps the rock with his hands and lifts or pulls upwards. The harder he pulls, the higher the rock is lifted. While he is lifting the rock, he feels pressure exerted on his hands and fingers--the more pressure his hands and fingers feel, the more force they are exerting to lift the rock.
For another example, if a woman wants to move a shopping cart, she places one hand on either end of the cart's bar handle. If she pulls with both hands, the cart moves towards her. If she pushes with both hands, the cart moves away from her. The amount of force she exerts in pulling or pushing the cart controls the speed in which the cart is moved. She can also control the direction in which the cart is pushed or pulled by varying the force exerted between her two hands.
The forces exerted by a person to control an object in a natural manner are multi-axial and/or multidimensional, and the displacement that occurs to an object is a result of the intended movement brought on by the application of an exerted force--displacement is the effect, not the cause of the intended movement.
Some devices that convert an applied force into electrical signals proportional to the applied force are known as evidenced by U.S. Pat. No. 4,495,219 issued to Sharp et al. However, the Sharp patent does not teach nor even suggest the benefits of and the natural manner in which a force actuated controller can be used to control motive devices. Additionally, the manner in which Sharp converts force to electrical signals is imprecise, subject to malfunction from wear-and-tear, and expensive to manufacture within the strict tolerance limits necessary to ensure proper operation.
Essentially, Sharp teaches two resistive layers with a spacer layer having a hole cut out. An elastomeric actuator positioned above the first resistive layer is pressed against the resistive layer which is then pressed against the second resistive layer when a force is applied to it. When a force is applied to the actuator, a connection between an area of the first resistive layer and the second resistive layer is made. The surface area covered by the connection is directly proportional to the force applied because the elastomeric properties of the actuator allow it to become deformed relative to the applied force.
One area in particular in which force can be used more naturally than displacement to control a motive object is the propulsion of a wheelchair. Without any sort of assistance, propelling a wheelchair can be an exhausting experience for anyone, regardless of their physical condition. Accordingly, many wheelchairs have small electric motors attached that allow the wheelchair to be propelled in response to the movement of a joystick or similar device.
In addition to the unnatural aspects that are a part of controlling the speed and direction a wheelchair moves with a joystick, somewhere between 5-10% of all wheelchair users lack the manual control and dexterity to accurately control and propel the wheel chair with a joystick. Some of the individuals in this population group suffer from diseases such as muscular dystrophy or partial upper body paralysis. For these individuals, precisely controlling the displacement and direction of the joystick is extremely difficult making it more difficult than usual for them to travel at the speed and in the direction they intend. Additionally, many of these same individuals are subject to muscle spasms, twitches, or similar ailments that further complicate the difficulties involved in using a joystick.